Buggy code:
public class CommitLog { private static final int MAX_OUTSTANDING_REPLAY_COUNT = 1024 ; private static volatile int SEGMENT_SIZE = ( 128 * 1024 ) * 1024 ; static final Logger logger = LoggerFactory . getLogger ( CommitLog . class ) ; public static final CommitLog instance = new CommitLog ( ) ; private final Deque < CommitLogSegment > segments = new ArrayDeque < CommitLogSegment > ( ) ; public static void setSegmentSize ( int size ) { } private final ICommitLogExecutorService executor ; private CommitLog ( ) { } public void resetUnsafe ( ) { } private boolean manages ( String name ) { } public static void recover ( ) throws IOException { } public static void recover ( File [ ] clogs ) throws IOException { } private CommitLogSegment currentSegment ( ) { } public CommitLogContext getContext ( ) { } public void add ( RowMutation rowMutation , Object serializedRow ) throws IOException { } public void discardCompletedSegments ( final Integer cfId , final CommitLogSegment . CommitLogContext context ) throws IOException { } private void discardCompletedSegmentsInternal ( CommitLogSegment . CommitLogContext context , Integer id ) throws IOException { if ( CommitLog . logger . isDebugEnabled ( ) ) CommitLog . logger . debug ( ( ( ( ( "discard<seq2seq4repair_space>completed<seq2seq4repair_space>log<seq2seq4repair_space>segments<seq2seq4repair_space>for<seq2seq4repair_space>" + context ) + ",<seq2seq4repair_space>column<seq2seq4repair_space>family<seq2seq4repair_space>" ) + id ) + "." ) ) ; Iterator < CommitLogSegment > iter = segments . iterator ( ) ; while ( iter . hasNext ( ) ) { CommitLogSegment segment = iter . next ( ) ; CommitLogHeader header = segment . getHeader ( ) ; if ( segment . equals ( context . getSegment ( ) ) ) { if ( CommitLog . logger . isDebugEnabled ( ) ) CommitLog . logger . debug ( ( ( ( "Marking<seq2seq4repair_space>replay<seq2seq4repair_space>position<seq2seq4repair_space>" + ( context . position ) ) + "<seq2seq4repair_space>on<seq2seq4repair_space>commit<seq2seq4repair_space>log<seq2seq4repair_space>" ) + segment ) ) ; header . turnOn ( id , context . position ) ; segment . writeHeader ( ) ; break ; } header . turnOff ( id ) ; <START_BUG> if ( header . isSafeToDelete ( ) ) { <END_BUG> CommitLog . logger . info ( ( "Discarding<seq2seq4repair_space>obsolete<seq2seq4repair_space>commit<seq2seq4repair_space>log:" + segment ) ) ; segment . close ( ) ; DeletionService . submitDelete ( segment . getHeaderPath ( ) ) ; DeletionService . submitDelete ( segment . getPath ( ) ) ; iter . remove ( ) ; } else { if ( CommitLog . logger . isDebugEnabled ( ) ) CommitLog . logger . debug ( ( ( ( "Not<seq2seq4repair_space>safe<seq2seq4repair_space>to<seq2seq4repair_space>delete<seq2seq4repair_space>commit<seq2seq4repair_space>log<seq2seq4repair_space>" + segment ) + ";<seq2seq4repair_space>dirty<seq2seq4repair_space>is<seq2seq4repair_space>" ) + ( header . dirtyString ( ) ) ) ) ; segment . writeHeader ( ) ; } } } void sync ( ) throws IOException { } class LogRecordAdder implements Runnable , Callable { final RowMutation rowMutation ; final Object serializedRow ; LogRecordAdder ( RowMutation rm , Object serializedRow ) { } public void run ( ) { } public Object call ( ) throws Exception { } } }

Fix:
if ( ( header . isSafeToDelete ( ) ) && ( iter . hasNext ( ) ) ) {